1. Field of the Invention
The present invention relates generally to surface mounted chip antennas, and more particularly to a surface mounted chip antenna, for easily performing impedance matching by forming a protrusion on at least one side portion of a feeding pattern, and adjusting distances between a radiation electrode and the feeding pattern, and between the feeding pattern and a ground electrode using the protrusion.
2. Description of the Prior Art
Generally, surface mounted chip antennas are used as antennas for small-sized communication devices, and have been recently popularized as global positioning system (GPS) antennas within mobile communication terminals. Typically, in a surface mounted chip antenna, a feeding pattern, a radiation electrode, and a ground electrode are formed on a rectangular hexahedral dielectric. The surface mounted chip antenna performs an antenna function by receiving high frequency (RF) signals through the feeding pattern, and radiating part of the high frequency signals into space using the radiation electrode.
FIG. 1 is a view showing a conventional surface mounted chip antenna 10. Referring to FIG. 1, the surface mounted chip antenna 10 has a dielectric block 2 made of a ceramic body or a resin. The dielectric block 2 is provided with a ground electrode 3 formed on a first major surface 2a of the dielectric block 2, a radiation electrode 4 formed on a second major surface 2b of the dielectric block 2, and a feeding pattern 5 formed on a region of the dielectric block 2 ranging from part of the first major surface 2a to part of its adjacent side surface. The radiation electrode 4 is especially formed to be spaced apart from the feeding pattern 5, and connected to the ground electrode 3 through two short portions 7 and 8 formed on different side surfaces. Further, the radiation electrode 4 has a length of xcex/4, where xcex is a wavelength of a resonance frequency.
In the surface mounted chip antenna 10, capacitance is formed between the feeding pattern 5 and the radiation electrode 4, and the radiation electrode 4 is excited by an inductance passing through the formed capacitance. In other words, the high frequency signal received by the feeding pattern 5 is transmitted to the radiation electrode 4 through the capacitance formed between the radiation electrode 4 and the feeding pattern 5. Then, the radiation electrode 4 resonates as a microstripline resonator, such that the part of electric field generated between the radiation electrode 4 and the ground electrode 5 is radiated into space. As described above, the surface mounted chip antenna 10 can be operated as a resonator antenna.
Further, as shown in FIG. 1, the two short portions 7 and 8 for connecting the radiation electrode 4 to the ground electrode 5 are formed on different side surfaces, and additionally serve to disperse a current density.
In such a surface mounted chip antenna 10, a resonance circuit is formed by the capacitance between the ground electrode 3 and the radiation electrode 4, and the inductance of the radiation electrode 4. In this case, the resonance frequency is adjusted by mutually coupling the radiation electrode 4 and the feeding pattern 5 using the capacitance between the radiation electrode 4 and the feeding pattern 5. However, the conventional surface mounted chip antenna 10 is disadvantageous in that it is difficult to adjust the resonance frequency because an electrode is previously formed on a surface through a designated patterning process so as to correspond to a predetermined resonance frequency.
Meanwhile, a ceramic body with a high dielectric constant (typically, a material having more than a dielectric constant of twenty) has been used as a material of the dielectric block to miniaturize the antenna. However, the ceramic body has a high specific gravity and a high material cost, such that it is undesirable to apply the ceramic body to antennas for mobile communication terminals. Further, the surface mounted chip antenna using the ceramic body with a high dielectric constant is disadvantageous in that it has a significantly narrow frequency bandwidth. Subsequently, as environment conditions of the antenna change, as when the mobile communication terminals are close to a human body, the operation frequency of the antenna is deviated from a usable frequency band, such that reception sensitivity of satellite signals rapidly decreases.
Therefore, in such antenna technological fields, there is required a new constructive surface mounted chip antenna for easily adjusting a resonance frequency and realizing miniaturization of the antenna even if the antenna uses a ceramic body with a low dielectric constant.
Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a surface mounted chip antenna, which has a protrusion on at least one side portion of its feeding pattern to easily perform impedance matching.
Another object of the present invention is to provide a surface mounted chip antenna, which has at least one conduction pattern on a side surface of a dielectric block to lower a resonance frequency or reduce antenna size.
In order to accomplish the above objects, the present invention provides a surface mounted chip antenna comprising a dielectric block constructed in the form of a rectangular solid having first and second opposite major surfaces; a ground electrode formed on the first major surface of the dielectric block; a radiation electrode for resonating at a predetermined resonance frequency, the radiation electrode comprising a radiation portion formed on the second major surface of the dielectric block and a short portion formed on at least one side surface of the dielectric block and used for coupling the radiation portion and the ground electrode; and a feeding pattern formed on at least one side surface of the dielectric block and spaced apart from the radiation electrode and the ground electrode, the feeding pattern having at least one protrusion on a portion adjacent to the radiation electrode.
According to a preferred embodiment of the present invention, the feeding pattern has a T shape, in which each protrusion is formed on both side portions of the feeding pattern, thus enabling an impedance matching to be easily performed. Further, if necessary, the protrusion of the feeding pattern can be formed to be extended to a side surface adjacent to the side surface on which the feeding pattern is formed.
Further, in another preferred embodiment of this invention, a through hole is formed for passing through opposite side surfaces of the dielectric block, and so the weight of the dielectric material is reduced. Further, the through hole can have a cylinder shape or a square pillar shape with a rectangular section.
Meanwhile, according to the present invention, the short portion of the radiation electrode, which is connected to the ground electrode, can be formed on any side surface not adjacent to the side surface on which the feeding pattern is formed.
Further, in another preferred embodiment of this invention, at least one conduction pattern is formed to be extended from the radiation electrode to some portion of a side surface of the dielectric block, or to be extended from the ground electrode to some portion of a side surface of the dielectric block, thus allowing the resonance frequency to be lowered by increasing capacitive coupling between the radiation electrode and the ground electrode, or the antenna to be further miniaturized in the case of same resonance frequency.